The lab has several ongoing projects with the aim of determining and characterizing the structure and immunogenicity of HIV-1 gp41 membrane proximal region. 1. Min Tang has several projects ongoing that relate to the MPR and to improvements of the Env PLs as immunogens and prime-boost strategies with the PLs, and has been invaluable using several expression systems to generate selected cores for structure. Also she has done some cellular assays which may have some value in interpreting immune response to different immunogens. a. Immunogenicity to determine if we can elicit antibodies against the gp41 MPR employing membrane ? various issues are being tested; is the MPR DNA immunogenic, MPR DNA+PADRE (heterolgous T cell help since we are not sure that the short MPR sequence contains a helper epitope), MPR PLs +PADRE?in combination with prime-boost of EnvPL gp160. b. With Barbara Capechi, prime-boost with Barbara?s bacterial expression system where large numbers of MPR repeats are presented in the outer membrane vesicles of bacteria. This is in progress in rabbits, should have some binding and neutralization data soon. c. Sequential boosting of EnvPL in order to drive what is commonly conserved between these clade isolates (CD4BS, gp41 MPR) and not the variable region-directed response. d. We have conducted studies including MPL or T helper lipopeptides into the PLs to enhance their immunogenicity. We have also changed lipids (more similar to the viral membrane composition) to enhance 2F5/4E10 binding. 2. Sanjay Phogat is working with the Hepatitis B surface antigen which form 22nM particles to present the MPR for binding and immunogenicity analysis. Production of high-levels of pure particles from baclovirus expression and yeast expression. 3. Javier Guenaga is examining the 2F5 epitope as defined by the Ofek-Kwong structure ?locked? onto selected protein scaffolds (in collaboration with David Baker) to be examined by production, binding, immunogenicity and structure. Since there seems to be an indication that prime-boost, coupled with cysteine-stabilization actually works, the likelihood of significant outcome has increased. Future activities within this project include cloning, bacterial and mammalian expression, refolding, ELISAs/Biacore, neutralization assays and integrating structural information into enhanced immunogen design.